3-Methyl- and 3-phenylisoxazol-5-acetic acids have been described by Micetich in Can. J. Chem. 48, 2006(1970), and the latter compound as well as its ethyl ester have also been reported by Kano et al., Jap. Pat. 6,814,216, June 15, 1968, Chem. Abs. 70, 20054u(1969). 3,4-Disubstituted isoxazol-5-acetic acids and 5-.alpha.-substituted acetic acids have been described in German Offenlegumgsschriften 2,155,081 (May 10, 1072) and its Divisions 2,166,467 and 2,166,468 (both Feb. 14, 1974), Chem. Abs. 77, 48483b(1972), 80, 108511h(1974), and 80, 108513k(1974), respectively, and equivalent to U.S. Pat. Nos. 3,891,635, June 24, 1975, and 4,010,264, Mar. 1, 1977; however, the compounds disclosed therein are distinguished from the compounds of this invention in having an aryl substituent only in position 3 while the substituent in position 4 is not an aryl group and is selected from H, lower alkyl, COOH, CONH.sub.2, CN, NH.sub.2, and Cl.
With regard to processes disclosed in the Prior Art it should be noted that an unambiguous process for preparing 3,5-diaryl- and 3,4,5-triarylisoxazoles has been described by Beam et al. in J. Org. Chem. 35, 1806(1970), and that the conversion of 5-methylisoxazoles to the corresponding isoxazol-5 -acetic acids and -5.alpha.-alkyl-acetic acids has been reported by Micetich, cited above.